Of course YGoHome did it the right way, but there are less intrusive ways to achieve your goal until he sends you the kit in the mail.
We solely used a back flush device at first. While is does have some attributes that work well, back flushing our tanks is difficult, because the actual tank is far up and away from this dump valve backflusing system—so it would take three to four backflush fill-ups to get the water to run clear.
That’s just too much time and water.
So we went to the old school method of running a flexible wand down the toilet and it has a rotating head that sprays water in a 360 circle to get the tank clean and the sensors as well.
Absent the mod by yGoHome, this is a good way to handle the waste, without “wasting” too much time trying to backflush. Amazon images included...
Also, because our gate valve is so much lower than the black tank, it does take a lot of water to get enough in the bottom of the tank to prevent a build up of solids. The first few flushes down the toilet just fill the gate valve and pipes leading to it.
I’m doing an experiment with an endoscope and a water gauge to find out exactly what the minimum water need to be to cover the bottom of the tank. Why? Because I’m still stuck here in SiP.
LASTLY, most experienced RVres will tell you to dump your black tanks first—it’s all over the internet. And while that is true, it’s best to let some great water out first, to make sure all of your sewer connections are tight, for obvious reasons. We once saw a guy empty his black tank all over his campsite when his hose came dislodged due to the high volume flush and he was watching the gate valve and not where it was SUPPOSED to go in the drain. And that’s another thing, always start opening the gate valves slower at first.